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Thread: wooden mast vs. aluminum

  1. #1
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    Default wooden mast vs. aluminum

    In Reuel Parker's book on cold-molded building he encourages building a wooden mast to accompany your wooden boat. He casts aspersions on the longevity of aluminum masts while stating that a well-built and well-maintained wooden mast can last for generations. Can anyone comment on this? I kind of like the idea of a wooden mast/boom but have a few questions. Specifically,
    1. How long does your average aluminum mast last before it needs to be replaced? Can an aluminum mast last for generations too?
    2. What maintenance in involved with a wooden mast?
    3. Wouldn't the extra weight of a wooden mast (compared to aluminum) make the boat less able to right itself in a knockdown? Would you have to have a heavier and/or deeper keel to compensate for the higher center or gravity?
    Thanks,
    Rick

  2. #2
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    Quote Originally Posted by rlawler View Post
    In Reuel Parker's book on cold-molded building he encourages building a wooden mast to accompany your wooden boat. He casts aspersions on the longevity of aluminum masts while stating that a well-built and well-maintained wooden mast can last for generations. Can anyone comment on this? I kind of like the idea of a wooden mast/boom but have a few questions. Specifically,
    1. How long does your average aluminum mast last before it needs to be replaced? Can an aluminum mast last for generations too?
    2. What maintenance in involved with a wooden mast?
    3. Wouldn't the extra weight of a wooden mast (compared to aluminum) make the boat less able to right itself in a knockdown? Would you have to have a heavier and/or deeper keel to compensate for the higher center or gravity?
    Thanks,
    Rick
    Aluminum masts can have corrosion problems.
    If it breaks it needs sophisticted equipment to repair.
    A wood mast needs care to preven rotting. If it breaks it can be repaired with low tech tools.

    A heavier mast is not necessarily bad. what matters is the weight from about halfway up. A heavy mast gives the boat a slower rolling motion. Very helpful to keep the crew from getting tired.
    Lets say you have an aluminum mast that weighs 5.5 lbs. per foot
    And you have the same size wood mast weighs 6.0 lbs. per foot.
    It is not a problem. If the mast is 50 feet tall then the extra weight difference would only be 12.5 lbs. heavier from halfway up.

    Also a round wood mast is aerodynamically better because no matter which way the wind is coming from the turbulance is the same-almost none. The aluminum mast if rectangle shape will have some turbulance (drag) from some angles.

    In a sudden gust the heavier mast is going to resist being pushed around. The lighter mast will react quicker to a sudden gust.
    I love the smell of fresh cut plywood in the morning.

  3. #3
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    Tripe!

    Both wood and aluminum masts can suffer from exposure to the elements. For aluminum masts, the principal trouble spot is where dissimilar metals are joined and it's relatively easy to keep these points sealed. Beyond that, all that's needed is an occasional waxing.
    Aluminum masts have an excellent record for longevity. As a practical matter, only a failure of standing rigging, a collision with a bridge or a roll-over will bring one down.
    From a cost point of view, the advange is to aluminum unless you already own the tree, don't put much value on your labor and are willing to accept the performance penalties of a heavier, bulkier spar.
    Aerodynamically, the designer of an aluminum spar has much more latitude in its shape and, for a given shape and stiffness, the aluminum spar can be slimmer and therefore more aerodynamically efficient.
    Other things being equal, light weight in a mast is always better. The effect of lighter weight is lower heeling moment and lower pitching moment. The first means that, for a given wind strength the boat with the lighter mast will heel less. The second means that in a given sea condition, the boat will be more able to go over a wave rather than plow through it.

    I could only justify wooden masts in a modern (not replica) boat for small daysailers.
    If the aesthetics of a non-wood spar are troubling, there's always the solution of the faux wood paint job, as Jon Wilson did on the carbon mast of his Concordia 33, Free Spirit.

  4. #4
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    I can't speak to how long, in general, aluminum masts last. I am pretty sure that the aluminum mast on my father's roughly 38 year old boat is original and it seems to be doing just fine. I know for certain that it has not been replaced since my father bought the boat back in about 1977. So, I am not real convinced that you should choose wood over aluminum for longevity reasons.

    The basic maintenance on a wood mast is keeping it finished and making sure water is not leaking in around fittings and the fasteners that hold them in place. Since masts take a beating from the sun and the running rigging, and have lots of fittings on them, they do need attending to.

    Yes, if the wooden mast is heavier (with the caveat noted by Donald that weight up high matters more than weight down low and because a wooden mast can be tapered you can lower the center of gravity) then, yes, it will cause the boat to heel more and make it harder to right the boat after a knockdown. When it comes to speed there is a reason why racing boats do not generally have wooden masts. On the other hand, the damping effect a wood mast has on rolling may have benefits in terms of comfort, but that damping effect comes at the expensive of stability.

    I have never seen a rectangular aluminum mast so I most presume Donald is talking about the typical oval/teardrop shaped aluminum mast. When the wind is blowing from the directions that matter most (typically the priority is put on windward ability) such a mast should produce less air turbulence than round mast. I see no reason why an aluminum mast couldn't be made round if that was in fact the more aerodynamically efficient shape. On the other hand, it would be pretty challenging to make a teardrop shaped wood mast.

  5. #5
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    Flag poles and parking lot light poles are nice tapered aluminum if you have an aversion to a straight stick. All of the masthead fittings could be welded as needed.
    As for turbulence in the lee of a round pole that is the subject in many text books. We have one boat owner who has his "Windex" mounted on a bracket below the mast head and when the wind is just right the pointer spins about 60 rpm.
    Last edited by ssor; 08-20-2007 at 04:04 PM.

  6. #6
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    Quote Originally Posted by Bruce Hooke View Post
    I can't speak to how long, in general, aluminum masts last. I am pretty sure that the aluminum mast on my father's roughly 38 year old boat is original and it seems to be doing just fine. I know for certain that it has not been replaced since my father bought the boat back in about 1977. So, I am not real convinced that you should choose wood over aluminum for longevity reasons.

    The basic maintenance on a wood mast is keeping it finished and making sure water is not leaking in around fittings and the fasteners that hold them in place. Since masts take a beating from the sun and the running rigging, and have lots of fittings on them, they do need attending to.

    Yes, if the wooden mast is heavier (with the caveat noted by Donald that weight up high matters more than weight down low and because a wooden mast can be tapered you can lower the center of gravity) then, yes, it will cause the boat to heel more and make it harder to right the boat after a knockdown. When it comes to speed there is a reason why racing boats do not generally have wooden masts. On the other hand, the damping effect a wood mast has on rolling may have benefits in terms of comfort, but that damping effect comes at the expensive of stability.

    I have never seen a rectangular aluminum mast so I most presume Donald is talking about the typical oval/teardrop shaped aluminum mast. When the wind is blowing from the directions that matter most (typically the priority is put on windward ability) such a mast should produce less air turbulence than round mast. I see no reason why an aluminum mast couldn't be made round if that was in fact the more aerodynamically efficient shape. On the other hand, it would be pretty challenging to make a teardrop shaped wood mast.
    Thanks Bruce.

    When i said "rectangular" I DID mean rectangular with rounded corners.
    On boats smaller than say 30 feet,the aluminum mast may be almost teardrop shape. A rectangle tube is 16% stronger than round.
    On boats 35 feet or larger they get more rectangular.

    In C.A, Marche's book "THE AEROHYDRODYNAMICS of SAILING"
    there are wind tunnel photos showing the round mast airflow.

    Also in a knockdown the wood mast wants to float.
    The aluminum mast may get water inside depending on how it was built.

    I have seen aluminum masts 20 years old and wood masts 20 years old. They both have problems.
    I love the smell of fresh cut plywood in the morning.

  7. #7
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    Quote Originally Posted by ssor View Post
    Flag poles and parking lot light poles are nice tapered aluminum if you have an aversion to a straight stick. All of the masthead fittings could be welded as needed.
    As for turbulence in the lee of a round pole that is the subject in many text books. We have one boat owner who has his "Windex" mounted on a bracket below the mast head and when the wind is just right the pointer spins about 60 rpm.
    I personally know of boats that have used tapered galvinized steel light poles and aluminum tapered flag poles. They both work.

    <a href="http://tinypic.com" target="_blank"><img src="http://i19.tinypic.com/63kfn15.jpg" border="0" alt="Image and video hosting by TinyPic"></a>
    Last edited by donald branscom; 08-20-2007 at 04:41 PM.
    I love the smell of fresh cut plywood in the morning.

  8. #8
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    Default Aluminum? Not long-lived? HOGWASH!

    Ever seen a much-abused Grumman Canoe (or other lesser brands) after twenty-some years?

    I once had an aluminum mast that had been salvaged by a friend on the end of his fishing line. No telling how long it had been submerged. I took it off his hands for twenty bucks, and fitted it with new shrouds, etc.

    It'd still be in-use by the current owner of the boat if I hadn't got it caught on an overhead power line and buckled it, requiring replacement by a NEW aluminum extrusion, which BTW, performed no better than the salvaged one. (Both mastds were fine for sailing)

    Wood WILL have to be refinished at intervals; closer intervals if finished bright.

    That said, there is an important aesthetic reason for considering wood; the TAPER. It is hard to find anyone these days who is willing to taper an aluminum mast. I believe most aluminum masts that have the same section all the way to the peak look TERRIBLE. Wooden masts are easy to build with a taper, Birdsmouth style, or otherwise.

    I presently sail one boat having a tapered aluminum mast and two having wooden masts. You should see the six coats of Deks Olje on my Melon Seed Skiff's mast.

    Moby Nick

  9. #9
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    Quote Originally Posted by Nicholas Scheuer View Post
    Ever seen a much-abused Grumman Canoe (or other lesser brands) after twenty-some years?

    I once had an aluminum mast that had been salvaged by a friend on the end of his fishing line. No telling how long it had been submerged. I took it off his hands for twenty bucks, and fitted it with new shrouds, etc.

    It'd still be in-use by the current owner of the boat if I hadn't got it caught on an overhead power line and buckled it, requiring replacement by a NEW aluminum extrusion, which BTW, performed no better than the salvaged one. (Both mastds were fine for sailing)

    Wood WILL have to be refinished at intervals; closer intervals if finished bright.

    That said, there is an important aesthetic reason for considering wood; the TAPER. It is hard to find anyone these days who is willing to taper an aluminum mast. I believe most aluminum masts that have the same section all the way to the peak look TERRIBLE. Wooden masts are easy to build with a taper, Birdsmouth style, or otherwise.

    I presently sail one boat having a tapered aluminum mast and two having wooden masts. You should see the six coats of Deks Olje on my Melon Seed Skiff's mast.

    Moby Nick
    I agree with what you say .
    But about those canoes.I see piles of those at the scrap yards.
    They are in excellent shape EXCEPT the bottoms are so thin from being dragged on the sand that tey are not worth repairing.
    A real shame.
    I love the smell of fresh cut plywood in the morning.

  10. #10
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    Quote Originally Posted by donald branscom View Post
    Thanks Bruce.

    When i said "rectangular" I DID mean rectangular with rounded corners.
    On boats smaller than say 30 feet,the aluminum mast may be almost teardrop shape. A rectangle tube is 16% stronger than round.
    On boats 35 feet or larger they get more rectangular.

    In C.A, Marche's book "THE AEROHYDRODYNAMICS of SAILING"
    there are wind tunnel photos showing the round mast airflow.

    Also in a knockdown the wood mast wants to float.
    The aluminum mast may get water inside depending on how it was built.

    I have seen aluminum masts 20 years old and wood masts 20 years old. They both have problems.
    I've spent most of my time on small boats, but the masts I've seen on larger boats are nowhere near as rectangular as the one you posted an illustration of in the next post, so I am not sure the comparison on airflow is really that fair. It seems like they are generally almost fully oval not rectangular.

    It is also worth noting that the reason most aluminum masts are deeper fore-and-aft than they are laterally is because the mast is better supported laterally by the shrouds than it is fore-and-aft via the stays. This means that you can make the mast thinner laterally than you could if the mast were round, which reduces weight and improves aerodynamics.

    It is a fair point that in a knockdown beyond 90 degrees a wood mast will want to float, which will add a little righting moment until the mast clears the water.

  11. #11
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    Default I should have qualified my comment about "abused aluminum canoes", Donald

    What I had in mind were a stable of Grummans bought in the late 1950's by a Boy Scout Council for replacing their venerable rack of wood and canvas conoes built by Pierre marquette and Old Town.

    The "new" Grummans are still in use, at least most of them. They are often "abused", but not nearly as badly as other canoes I've seen available for rent on rocky creeks in S Indiana, which might be lucky to last ten years.

    Moby Nick

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